Update nested-query.asciidoc
Update nested-query.asciidoc

Removed reference to `filter` from the nested query docs

Relates to #15648
strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test,strapdata/elassandra-test